NOTE: This is work in progress! The interface may change from version to version.

A Python module of Half-Life physics routines for research and experimentation purposes.

$ pip install pystrafe

The following examples illustrate different situations one might encounter. In each example, pystrafe is used to aid planning and validation of run strategies by solving computational problems.

There is a gap of 1000 units wide that can save 30s from the run if leaped across. The difference in player position at the starting (standing) and ending (ducking) position is merely 100 units. You are playing at 100 fps and default settings. Unsure if a TAS bot can make the jump, let alone a human player?

>>> from pystrafe import motion, jumpspeed
>>> K = motion.strafe_K_std(0.01)
>>> dist, height = 1000, -100
>>> gravity = 800
>>> motion.strafe_solve_speedxi(jumpspeed, K, dist, height, gravity)
1046.7786535278178

Looks like you need at least 1046 ups at the moment you jump to make it across the gap!

Note: the height variable is declared -100 rather than 100, because the final position is at a lower position than the starting point.

There is a gap 700 units wide and the solid ground ahead is 200 units below the current position. You have very low health and a grenade, and running towards the gap at 100 ups. How would you damage boost across the gap while minimising the health loss? Boost horizontally? Boost towards the opposite edge? Boost at an upward angle?

>>> from pystrafe import motion, jumpspeed
>>> K = motion.strafe_K_std(0.001)
>>> vel = [100, jumpspeed]
>>> dist, height = 700, -200
>>> gravity = 800
>>> dv = motion.solve_boost_min_dmg(vel, K, dist, height, gravity)
>>> dv
[172.28574486554757, 218.8998258941578]
>>>
>>> # Calculate the health required and angle of boosting!
>>> from math import hypot, atan2, degrees
>>> hypot(dv[0], dv[1]) / 10   # 10 because of ducking
27.856688902374805
>>> degrees(atan2(dv[1], dv[0]))
51.79538244723009

Turns out you must launch yourself upwards at about 52 degrees and lose about 28 HP at the bare minimum! The answer is often slightly surprising, and non-trivial to work out by yourself, but you can trust the results computed by pystrafe.

You are curious how long the jump itself will take to get to the other side.

>>> motions.strafe_time(dist, vel[0] + dv[0], K)
1.5422678575586732

That is about 1.54 seconds. Now you can decide if you would like to cut this down further by applying more damage to the boost. Remember, the about 278 damage calculated earlier is the minimum required!

From the previous section, we computed that we need to lose 28 HP. Unfortunately, the grenade has to be placed very close to us. You decided to acquire some more armour to survive a closer grenade blast. How much do you need?

>>> from pystrafe import damage
>>> damage.ap_dhp_damage(28, 80)
(25.5, 26.0, '(', ']')

We need to acquire AP in the range of (25.5, 26] to obtain the desired health loss.

There exists a perfect, minimal-time route from start to finish in any game, including Half-Life and its expansions, known only to the gods. This Python module cannot be used to discover that route! At least not in its entirety.

The underlying physics is documented separately at https://www.jwchong.com/hl/.